title: Ventilatory response to added dead space and position in preterm infants at high risk age for SIDS.
abstract: OBJECTIVE
  The vulnerability of prematurely born infants to sudden infant death syndrome (SIDS) in the prone position might be explained by a reduced ability to respond to a stress, such as hypercarbia, in that position; our objective, therefore, was to further explore the influence of position on the response to a stress.
  
  
  OBJECTIVE
  The ability of prematurely born infants to respond to added dead space in the prone compared to the supine position would be impaired at the high risk age for SIDS.
  
  
  METHODS
  Twenty infants, median gestational age of 30 (range 24-32) weeks were studied at a median postmenstrual age (PMA) of 45 weeks. In addition, comparisons were made to the results of 25 infants studied at 36 weeks PMA.
  
  
  METHODS
  Infants were studied supine and prone. Breath by breath minute volume was measured at baseline and after a dead space was incorporated into the breathing circuit; the time constant of the response was calculated. The pressure generated in the first 100 msec of an occlusion (P0.1 ), the maximum inspiratory pressure during an airway occlusion and functional residual capacity (FRC) were also measured in both positions.
  
  
  RESULTS
  The median time constant was longer (38 (range 15-85) vs. 26 (range 2-40) sec (P = 0.002)). P0.1 lower (P = 0.003) and FRC higher (P = 0.031) in the prone compared to the supine position. In the prone position, the time constant correlated with PMA (P = 0.047), that is, the rate of response to added dead space was significantly damped with increasing postnatal age up to the critical age for SIDS.
  
  
  CONCLUSIONS
  The dampened rate of response to added dead space in the prone compared to the supine position lends support to the hypothesis that a poorer response to a stress may contribute to prematurely born infants increased risk of SIDS in the prone position.
authors.affiliation: Division of Asthma, Allergy and Lung Biology, MRC-Asthma Centre, King's College London, London, United Kingdom.
authors.forename: Tolulope
authors.initials: T
authors.lastname: Saiki
authors.forename: Simon
authors.initials: S
authors.lastname: Hannam
authors.forename: Gerrard F
authors.initials: GF
authors.lastname: Rafferty
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Milner
authors.forename: Anne
authors.initials: A
authors.lastname: Greenough
mesh_terms: D005260:Female; D005652:Functional Residual Capacity; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D011187:Posture / Q000502:physiology*; D016684:Prone Position; D012126:Respiratory Dead Space; D013398:Sudden Infant Death / Q000209:etiology*; D016683:Supine Position
keywords: functional residual capacity; prematurity; respiratory control; respiratory muscle strength